Process for preparing moldable thermoplastic polymer particles

ABSTRACT

Thermoplastic polymers can be treated directly with an organofunctional silane coupling agent and a resinous copolymer of ethylene and acrylic and/or methacrylic acid so as to enhance their bonding to inorganic oxide substrates thereby providing moldable products with superior physical properties heretofore unattainable.

United States Patent Elder, Jr.

[54] PROCESS FOR PREPARING MOLDABLE THERMOPLASTIC POLYMER PARTICLES [72] Inventor: John A. Elder, Jr., Plainfield, NJ.

[73] Assignee: Union Carbide Corporation, New York,

[22] Filed: Oct. 9, 1969 [21] App1.No.: 865,188

[52] U.S.Cl. ..117/100 C, 1 17/161 UC, 117/161 UT,

117/161 ZA, 260/41 R, 260/41 AG [51] Int. Cl ..B44d 5/00 [58] Field ofSearch ..ll7/100C, 161 ZA, 161 NT, 117/161 UC [56] References Cited UNITED STATES PATENTS 2,976,148 3/1961 Walford ..1 17/161 [451 Mar. 21, 1972 Primary Examiner-William D. Martin Assistant Examiner-Mathew R. P. Perrone, Jr. AttorneyPau1 A. Rose, George A. Skoler and Aldo John Cozzi [5 7] ABSTRACT Thermoplastic polymers can be treated directly with an organo-functional silane coupling agent and a resinous copolymer of ethylene and acrylic and/or methacrylic acid so as to enhance their bonding to inorganic oxide substrates thereby providing moldable products with superior physical properties heretofore unattainable.

6 Claims, No Drawings PROCESS FOR PREPARING MOLDABLE THERMOPLASTIC POLYMER PARTICLES This invention relates to the treatment of thermoplastic polymers to enhance their bonding to inorganic surfaces. More particularly, this invention relates to the treatment of thermoplastic polymers so as to enhance their bonding to inorganic oxide substrates and to provide thermoplastic polymers filled with such inorganic oxides. I

There has been described in the literature and patents procedures for filling thermoplastic polymers with inorganic oxides. In the initial development 'of such art, treated inorganic oxide materials, particularly in'particulate form, were introduced and blended into thermoplastic polymers and the resulting mixtures were molded by conventional methods such as casting, injection molding, extrusion, rotational molding and the like, to form inorganic oxide reinforced plastic articles. However, it had been found that the properties of such filled articles, though improved over the plastic per se, did not meet the quality level which the art expected and desired. Then the art attempted treatment of such inorganic oxide particulate material for the purpose of enhancing its bonding relationship with respect to the thermoplastic polymers. One treatment involved coating the inorganic oxide polymer material with silicone coupling agents, that is, the hydrolyzates of the well known silane coupling agents. This treatment lended some improvement in the properties of the composite structure but, again, did not yield the properties believed possible from this type of system.

This invention involves a new concept in the formation of such composite system wherein the treatment effected for the purpose of enhancing the bonding relationship between the thermoplastic polymers and the inorganic oxide is achieved by a special treatment of the polymer itself rather than the artdirected effort to treat the inorganic oxide first. This invention involves supplying upon the surface of a thermoplastic polymer an organo-functional silane coupling agent and a resinous copolymer of ethylene and acrylic acid and/or methacrylic acid. It has been determined that such a treated polymer when blended and molded in combination with particulate inorganic oxide yields significantimprovements in processing and properties over the methods heretofore employed which involved treatment of the inorganic oxide surface.

The thermoplastic polymers treated in accordance with this invention are any of those having sufficient molecular weight and flow characteristics to be molded by such conventional means such as described above. "Particularly preferred polymers are the olefin polymers such as polyethylene (high and low density), polypropylene, po'ly-l-butene, polystyrene, poly-a1pha-methylstyrene, polybutadierie-LS, and the like. Other useful polymers employable in the practice of this invention include polyvinylchloride, polyvinylacetate, polymethylmethacrylate, polyethylacrylate, copolymers of styrene and acrylonitrile, block copolymers of acrylonitrile and butadiene-l,3, terpolymers of butadiene-l,3, styrene and acrylonitrile, nylons (such as polyhexamethyleneadipamide, polytetramethylenesebacamide, polyepsiloncaprolactam, and the like), the polyimideazolines, polyesters (such as polyethyleneterephthalate, polyl ,4-cyclohexyleneterephthalate, and the like), the oxy-methylene homopolymers and copolymers (the polyformaldehyde polymers), polycar bonates such as the reaction product of phosgene or monomeric carbonate esters with bis-Phenol A [2-bis(4- I hydroxphenyl)propane], and the like, polyarylene polyethers such as described in US. Pat. No. 3,264,536, patented Aug. 2, 1966, and the like.

The organofunctional silane coupling agents suitable for use in the practice of this invention comprise those which are condensable with the carboxy group of the ethylene-acrylic and/or methacrylic acid copolymers. These organo-functional silanes are those which on hydrolysis and condensation form siloxanes characterized by repeating unit formula: v H W wherein X is a functional group which is condensable with a carboxylic acid group, e.g., functional groups such as HS-, HO-, O C N-, and the like; and R is a saturated hydrocarbon radical containing at least three carbon atoms in sequence therein separating X from Si and bonded to both, provided that when X is R may contain two carbon atoms in sequence separating the HS- from Si. These siloxanes are obtained by the hydrolysis and condensation of silanes such as those encompassed by the formula:

XR'SiY wherein Y is any hydrolyzable group such as alkoxy, aroxy, halogen, amino, and the like. It should be understood that in the case of the silane where X is O C N, the same functional group is not to be found in the siloxane since isocyanates are unstable to hydrolysis. However, the reaction product of isocyanate with water forms which is a functional group pursuant to this invention. The isocyanate group can be put into the siloxane by phosgenation of CIEECHzSKOCHz);

notcflorsltoomh HiNCHICHI H (C |)t (0C a)a (HOCEICH|)IN(CH2):S1(O CHICHQ;

HSCHQOHICHBSKOCHI)! HBCHzCHISKOCHt)! O H N NIHCHQaBKOCHOx The silanes containing ester groups in the organic radical are believed capable of providing hydroxyl groups by in situ hydrolysis of the ester groups during curing of the ethyleneacrylic and/or methacrylic acid copolymer on the substrate.

The ethylene-acrylic and/or methacrylic acid copolymers employed in the practice of this invention are described in US. Pat. No. 3,264,272, patented Aug. 2, 1966 and US Pat. No. 3,321,819, patented May 30, 1967. Though these patents are directed to the salt form of the copolymers, it is to be understood that in the practice of this invention the free acid copolymers and the salt form thereof may be employed. Moreover, in the practice of this invention one may employ a copolymer containing a low concentration of polymerized acrylic and/or methacrylic acid. In the practice of this invention acrylic and/or methacrylic acid content may be as low as about 5 weight percent based on the weight of the copolymer. Preferably, the copolymer contains at least about 14 to about 55 weight percent, based on the weight of the copolymer of the polymerized acrylic and/or methacrylic acid. Most desirably, the copolymers do not have a melt index greater than about 200 as expressed in the decigrams per minute most preferably not greater than about 100. The remaining weight of the copolymer is, of course polymerized ethylene.

For the purpose of describing the invention, emphasis has been made to a copolymer of three potential ingredients, to wit, ethylene, acrylic acid and methacrylic acid. However, for the purposes of scope, this invention is not limited to just this class of copolymers. Broadly speaking, the copolymer can be expressed as a polymer of an alpha-olefin having the general formula RCHZCl-l wherein R is a radical selected from the group consisting of hydrogen, alkyl radicals having from one to eight carbon atoms and phenyl. The acrylic acid and/or methacrylic acid can be substituted for in part or completely by other alpha, beta-ethylenically unsaturated carboxylic acids, preferably having from three to ten carbon atoms therein. In addition to the two acids mentioned previously herein, there is included, by way of example, ethacrylic acid, itaconic acid, maleic acid, fumaric acid, 9-decenoic acid, and the like. The copolymer may be made originally from the respective anhydrides of the above acids or from the acid itself. lt is to be emphasized for the purposes of this invention the use of acrylic and/or methacrylic acid are highly preferable but by no means is this invention restricted by this selection. Thus any of the alpha, beta-ethylenically unsaturated carboxyl acids as defined above, which term includes acrylic and methacrylic acids, can be advantageously employed. As mentioned previously, the copolymer can be at least partially saponified with a monovalent base before use. The degree of saponification, when saponified, should be at least sufficient to cause the polymer to be more soluble in water. The above limits on the amount of saponification are not intended to be so restrictive because in the operative practice of this invention the amount of saponification should be determined as that amount which allows dissolution in water at 100 C. of at least about 25 weight percent of the copolymer.

The silane coupling agents and the ethylene-acrylic acid copolymers can be provided at a surface of the thermoplastic polymer particles in many ways. One method involves depositing particles of the polymer into liquid baths of the silane and ethylene-acrylic acid copolymer or into liquid baths comprising a mixture of the two. Such method does not lend itself to good control of the concentration of the components on the surface of the polymer. Another method which may be employed involves tumbling the thermoplastic polymer in a closed vessel and injecting the silane and the ethylene acrylic acid copolymer therein alone or in admixture in the form of liquids. Such injection may be effected by a thin stream or through use of a spray nozzle. Preferred results are obtained when a mixture of the silane and the copolymer are sprayed into the tumbled particles. Another method for incorporation of these treating components on the surface of the polymer particles involves introducing these components separately or together into an inert gas stream such as carbon dioxide, nitrogen, methane, argon, and the like; and feeding said stream into a cylinder comprising a bed of the polymer particles to effect fluidization thereof. Conventional fluidization procedures and apparatus maybe employed. It is evident that the fluidization procedure readily lends itself to a continuous operation scheme.

It is preferred that in the operation of such fluidization treatment that one can control the amount of the treating component to be introduced into the bed so as to avoid the presence of such components in the offgas leaving the bed.

The treating components may be provided neat or in solution or suspension using solvents or non-solvents as the ease requires. The treating components may also be supplied to the polymer particles as a molten mixture, preferably so in the case of ethylene-acrylic acid copolymer. Since the silane is a liquid at treating conditions, there is no difficulty in coating the polymer particle with this material. However, in the case of the ethylene-acrylic acid copolymer it is often necessary to liquefy it either by melting or by solution with a solvent therefor or by dispersing particles thereof in a solvent medium. The copolymers may also be converted into a salt form and this readily enhances the solubility of the copolymer in water, allowing it to be more easily dispersed therein. Illustrative of such salts are the ammonium salt, amine salt, and alkali metal salt. The preferred salt form is the ammonium salt.

To obtain the desired results, the amount of the silane coupling agents provided on the surface of the polymer particles does not exceed about 1 percent by weight of the polymer particles being treated and preferably is not less than about 0.01 percent based on the weight of the polymer particles. Usually, at least about 0.1 weight percent of the silane is supplied to the polymer surface. In some cases, not more than about 0.07 weight percent of silane is required. The silane can be supplied to the particles in the form of its hydrolyzate, produced by mixing the silane in an aqueous medium.

The ethylene-acrylic acid copolymer, per se, or any salt form thereof, is desirably used in very small amounts. Typically not more than about 1.0 weight percent of the copolymer, based on the weight of the polymer particles being treated, is provided thereon. It is possible to obtain beneficial results using amounts of copolymer as little as about 0.01 weight percent, based on the weight of the polymer particles. Preferably, one employs an amount of copolymer in the range of from about 0.1 to about 0.6 weight percent based on the weight of the polymer particles.

As is already known in the art, an inorganic oxide-reinforced plastic exhibits increased flexural strength and improved heat resistance. lllustrative of such inorganic oxide are glass fiber, preferably cut to a length not more than about onehalf inch, siliceous fillers (such as hydrated silica, silica aerogel, fume silica, and the like), aluminum silicates, titanium dioxide, magnesium silicate, magnesium aluminum silicates, whiting, and the like. In the usual practice organic oxide particles, other than glass fiber, are typically blended into the molten plastic resin and the filled resin is then extruded and cut into particles which are molded to the desired shape. In the case of glass fiber, particles of the resin are dry blended with the glass fiber and through molding, a shaped product is formed. It has been determined that when the treated polymer particles, as described previously, are blended in the aforementioned inorganic oxide and then subjected to molding conditions under sufficient heat to effect fusion of the polymer particles, significant advantages are obtained, such as improvement in flexural strength and substantial improvement in the heat distortion characteristics of the shaped article.

It has been determined that when treatment, such as described above, is given to the glass fibers rather than to the polymer particles and the mixture of all such particle components is achieved under a substantial shear force, such as in a screw injection molding machine, a substantial amount of the glass fiber bundles are not effectively dispersed, thereby adversely affecting the appearance of the sheet as well as its physical properties.

The explanation for the above result appears to occur because of the manner in which the fiber is provided by glass fiber producers. In the manufacture of glass, continuous multiple filaments of glass are formed from a bushing and these continuous multiple filaments are gathered up as a bundle. Then the bundles are cut into desired lengths to form bundles of staple glass fibers. When this glass fiber is treated with the silane coupling agent or its hydrolyzate and the ethyleneacrylic acid copolymer, and the resulting treated glass fiber bundles are mixed under substantial shear forces with particles of thermoplastic polymers there is noted a separation effect whereby bundles of the glass fiber develop on the surface of the extruded plastic article adversely affecting its ap-v pearance and to some extent adversely affecting its physical properties. However, when the treatment of silane or its hydrolyzate and the ethylene-acrylic acid copolymer is coated on the polymer particles rather than on the glass particles, such effect is not apparent and intimate dispersion of the glass fibers through the polymer matrix is achieved to produce an extruded plastic article having a smooth exterior and having the desired improvement in flexural strength and heat distortion noted above.

In order to characterize this invention with regard to specific embodiments thereof reference is made to the following examples. it is not intended that these examples shall in any way act to limit the scope of this invention. in the following examples the abbreviation min. is for the term minute and all values for melt index are given in decigrams per minute at 190 C.

EXAMPLE l A 150 gram masterbatch consisting of 102.2 grams of high density polyethylene, in powdered form as received from the polymerization reactor, having a melt index of 9.2 (decigrams/min. at 190 C.) and a density of 0.958; 25.3 grams of ethylene-acrylic acid copolymer (in pellet form) containing percent acrylic acid per weight of polymer having a melt index of 50 (decigrams/min. at 190 C and a density of 0.96 with an ultimate tensile strength of 2,100 p.s.i. (ASTM D-638-64T) and 22.5 grams gamma-me thacryloxypropyltrimethoxysilane was prepared by first softening the polyethylene at a temperature of 120 C. on a two roller roll mill and incorporating the other ingredients. This composite was removed from the roll mill in sheet form having an approximate thickness of one-eighth inch. The sheet was rendered brittle with dry ice, shattered, fed to a grinding mill (packed in dry ice) and ground to a powdered form.

A 46.6 gram portion of this masterbatch was blended with 1,354 grams of high density polyethylene, in powdered form as received from the polymerization reactor, and 600 grams of chopped fiberglass having an average fiber length of onefourth inch. a filament diameter of 0.00051 inch having 200-400 filaments per bundle, for 5 minutes in a horizontal drum blender, allowing 50 percent free space. The 2,000 gram.

batch (hereinafter designated Batch 1) was then fed to a 3 ounce single-screw, reciprocating injection machine to mold standard ASTM tensile, fiexural and impact test specimens. 7

TABLE 1 Flexural l Flexural Izod Heat 0 strength modulus in act deflection (p.s.i.) (p.s.l) (IL-lb. in.) 0.)

Batch 1 10, 200 670, 000 2 0 122. 6 6, 900 1. 5 100. 4 9, 650, 000 2. 0 96- 6 LASTM D-790-66 04 x 5" x 5" specimen, rate 0.2 1n./m1n.)-secant modulus measured at point of 0.1 inch deflection.

1 Same as Note 1.

8 ASTM D-256-56 (54" notch).

ASTM D-648-fi6 04 x 36" x 5" specimen, 264 p.s.i.).

EXAMPLE 2 This example demonstrates the application of ethyleneacrylic acid copolymer and gamma-methacryloxypropyltrimethoxy-silane co-ingredients directly on the surface of high density polyethylene, thereby eliminating the need for incorporation by roll milling and consequential grinding.

Firstly, a suspension, hereinafter designated Suspension A, was prepared by dispersing 70 grams of a 20 weight percent solids ammoniacal dispersion (pH 9.0) of ethylene-acrylic acid copolymer containing 20 percent acrylic acid per weight of polymer (melt index of 50, density 0.96, ultimate tensile 2,100 p.s.i.) in 210 cc. of water. Secondly, a solution, hereinafter designated Solution B, was prepared by co-mixing 12.5 grams of gamma-methacryloxypropyltrimethoxysilane with 200 cc. of petroleum ether (Boiling range 3760 C.).

Suspension A was uniformly sprayed on 1,374 grams of high density polyethylene as set forth in Example 1. The treated polyethylene was dried in an oven at 77 C. Thereafter Solution B was uniformly sprayed on the treated polyethylene and the petroleum ether and residual water were allowed to evaporate. The resultant dried polyethylene weighed 1,400 grams.

The 1,400 grams of treated polyethylene were dry blended with 600 grams of chopped fiberglass and the blend was injection molded to standard ASTM test specimen as previously described in Example 1. This batch is hereinafter designated Batch 4.

The above process was repeated to produce a batch containing no ethylene-acrylic acid copolymer and no gammamethacryloxypropyltrimethoxysiloxane; this batch is hereinafter designated as Batch 5.

A comparison chart of the relevant physical properties of measured at point of0.1 inch deflection.

Same as Note 1.

'ASTM D-25 6-56 inch notch) "ASTM D-648-56 (AXEfiXS inches specimen, 264 p.s.i.)

EXAMPLE 3 To demonstrate the combined effect of various proportions 2 .e "!we e??? 9a 9x225?pyl riestkssyelaps assua e.

acrylic acid copolymer on resultant physical properties of different grades of polyethylene filled with fiber glass, several batches were prepared employing the following procedure.

A 1,400 gram batch of high density polyethylene, as

solids ammoniacal dispersion of ethylene-acrylic acid (pH 9.0) and 2.45 grams of the gamma-methacryloxypropyltrimethoxysilane. This batch was blended with chopped fiberglass, as described in Example 1, and the blend injection described in Example was Stirred in a Hehsehel mixer and molded into specimens in the manner set forth in examples I, measured quahhhes, Stated the Tables below, of y e 2 and 3. These specimens are hereinafter referred to as Samacrylic acid copolymer and gainma-methacryloxypropyll 2,

trimethoxy-silane were sprayed therein, as described in Exam- A hi d b h of polypropylene was prepared i h great. P y 'y p y was'ln the form of an ment with either ethylene-acrylic acid copolymer or gammaaqlleous p f i as prevlously descrlbed Example methacryloxypropyltrimethoxysilane. This untreated batch After SPraymg complete, the treated P y y was was blended with chopped fiberglass as described in Example O 0 n i n dried Y an oven at 77 for 18 hours- The (med 1; the blend in ection molded in the manner set forth in Exam- P ye y was blended Whh 600 grams of pp fiber pics 1, 2 and 3, and the specimens hereinafter referred to as glass in a horizontal drum blender, the blend was then injec- S l 3} m e standard ASTM test Speclmehs as Previously Table 4 compares the physical properties of the three samdescribed in Examples 1 and 2. P165 The results of several batches employing three qualities of TABLE 4 high density polyethylene are tabulated below. 7

Flexural" Flexural" Heat- TABLE 335 Strength Modulus Izod- Deformation Heat No. (p.s.i.) (p.s.i.) (ft.|b./in. (C.) Silane EAA Flexurai Flexural 1 defor- (wt. (wt. strength modulus Izod matlon 1 10.000 620. .0 I481 percent) percent) (p.s.i.) (p.s.i.) (it. 1b./in.) C.) 2 10.000 685.000 3.5 149.1

ASTM D-790-66 (/cX'yiXS inchcsspecimcn, rate 0.2 in./min.) secunt modulus 0. 35 0. 4 12, 500 010, 000 2. 5 121 measured at point ofO.l inch deflection.

0 0 6, 00 000 3 4 'Same as Note I.

'MsTM 'o zso-se 0* inch notch). TABLE -ASTM D-648-56 vi vzxs inches specimen, 264 p.s.i.). EAA F i F1 1 Silane lexura exura e or- (wt. (wt. strength modulus Izod matlon H EXAMPLE percent) percent) (p.s.i.) (p.s.i.) (it. lb./ln.) C.) crein presented is a chart comparing the physical proper- 0 4 13 400 690,000 3.1 122 ties of molded products; the first sample therein treated with .175 0.2 13,900 680,000 2.9 125 gamma-aminopropyltrimethoxysilane, and the second sample 0 0 wo'ooo 117 35 therein treated with gamma-methacryloxypropyltrimethox- TABLE 30 ysilane.

Heat, The method employed to produce said samples is that Silane EAA Flexural l Flexural 2 deiormethod reviousl described in Exam le 3.

(wt. (wt. strength modulus Izod mation p y p percent) percent) (p.s.i.) (p.s.i.) (it. 1b./in.) C.) 40 TABLES 5 0- 35 4 300 1 0 124 Flexural 1 Flexural 2 Heat '3 g'% Silane EAA Strength Modulus Izod Deformation 1 i (wt. (wt. (psi) (psi) (ft. lb./in.) (C.)

l ASTM D-790-66 (%x}x5 specimen, rate 0.2 in.lmiu.)-secant mogulus melaIsutrerli at point of 0.1 inch deflection. 0.31 0.4 10,800 698,000 1.6 1204 1 me as o e 0.35 0.4 13,300 0,000

X X S 60 men, .5.

5 Table density polyelghylene, meltpmdex of i0, density of ASTM D-790-66 (/p X /2 X5 SPCCIITICIL rate 0.2 inJminJ-seCant modulus (L962. measured at point of0.l inch deflection.

B Table 3b.high density polyethylene, melt index of 16.0, density 0! 2 Same as Note 1.

0.955. 1 ASTM D-256-56 (*l." notch).

1 Table 3c.high density polyethylene, melt index of 19.0, density of 4 ASTM 064856 (WX i snspecimeny 264 h l a methzlaicrylqypropf ltr i fiyi g d i I 1 t i High density oolyethylenc. melt index of 4.0.dens ity of0.962.

t yene-acry 0 ac copo ymer me n ex: ec grumsm n. 11

0 OJ containing 20 percent acrylic acid per weight of polymer. In the aforementioned examples all weight percentages for silane and ethylene acrylic acid copolymer are based on the EXAMPLE 4 weight of resin present in the sample. What is claimed is:

This example demonstrates enhanced physical properties of 1 A process f preparing moldable thermoplastic polymer P Strength and heat of glass fiber finefj particles which comprises depositing on the surface of therpolypropylene when treated with silane and ethylene-acrylic l ti polymer particles; acid copoly a. from about 0.01 to about 1 percent by weight, based on Firstly, 28 grams of anammoiiacal dIISPCISlOH lolf 2900weight the weight of the polymer particles of an organofuno P cent ethylene'acryhc copo ymer (P was tional silane, or the hydrolyzates and condensates sprayed on 1,400 grams of stirred powdered polypropylene thereofsaid silane having the formula.

(Shell-5520, melt index 5; sold by Shell Chemicals Co., Shell XR'SiYa Oil Ne York, New York) In a eohhhuously operated wherein X is a functional group which is condensible with a Hensch l mlx e yi grams of gamma'meihacrylox' carboxylic acid group and R is a saturated hydrocarbon radiypmpyhnmethoxysllane e umformly f lf on h Stirred cal containing at least three carbon atoms in sequence therein p yp ep After Spraying Vlgorous surfing commuefi for separating X from Si and bonded to both, provided that when PP l) l The s Polypropylene Pamdes X is HS-, R may contain two carbon atoms in sequence were oven dned for 18 hours at 77 C separating the HS- from Si and Y is a hydrolyzable group; and

The reeled P yp py was then l d h 600 b. from about 0.01 to about 1 percent by weight, based on grams of commercial chopped fiberglass as described in Exthe weight of the polymer particles of a copolymer of an ample P the blend mlecuon molded to Standard alpha-olefin, and an alpha-beta-ethylenically unsaturated ASTM specimens, as previously set forth in Examples 1, 2 and carboxylic acid.

3; and these specimens hereinafter referred to as Sample 1." The process of claim 1 wherein (b) is a copolymer of A second batch of treated polypropylene was prepared using the preceding method with 14 grams of the 20 per cent ethylene and acrylic acid.

3. The product formed by the process of claim 1. 

2. The process of claim 1 wherein (b) is a copolymer of ethylene and acrylic acid.
 3. The product formed by the process of claim
 1. 4. The product produced by the process of claim
 2. 5. The product produced by the process of claim 2 wherein (a) is gamma-methacryloxypropyltrimethoxysilane.
 6. The product produced by the process of claim 2 wherein (a) is gamma-aminopropyltriethoxysilane. 